This invention relates in general to reflectance determination and, more particularly, to a portable system and method for determining one or more reflectance properties of a surface.
The ability to accurately evaluate reflectance properties of an object or a surface has become increasingly important. Reflectance properties may, for example, influence radar measurements or other visibility characteristics of an aircraft or other object. One problem associated with reflectance measurement systems is the inability to obtain reflectance property values quickly and accurately. In addition, reflectance measurement systems generally lack flexibility in adapting to various environments as the measurement systems are generally stationary laboratory instruments, which preclude in-situ measurements of an object or a surface.
The present invention provides a system and method for determining one or more reflectance properties of a surface that substantially reduce or eliminate problems and disadvantages associated with the previous systems and methods.
In a particular embodiment, the present invention provides a method for determining one or more reflectance properties of a surface using a portable apparatus that includes reflecting a first beam of electromagnetic energy off of a measured surface, the first beam contacting the measured surface at an angle that is near normal to the measured surface. The method also includes reflecting a second beam of electromagnetic energy off of the measured surface, the second beam contacting the measured surface at an angle that is near grazing to the measured surface. Reflected portions of the first and second beams of electromagnetic energy are then collected and at least one reflectance characteristic value associated with the measured surface is determined based on the reflected portions of the first and second beams of electromagnetic energy.
In accordance with another embodiment, an electromagnetic energy controller is provided for a portable measuring apparatus that comprises a chopper operable to transmit a first portion of electromagnetic energy toward a first reflecting element and to reflect a second portion of electromagnetic energy toward a second reflecting element and to absorb a third portion of electromagnetic energy. The chopper executes a repetitive cycle in which the chopper transmits, reflects, and then absorbs portions of electromagnetic energy. The first and second portions of electromagnetic energy are reflected by the first and second reflecting elements respectively toward a surface plane. An integrator receives reflected electromagnetic energy from the surface plane that is communicated to a processor, the processor being coupled to the integrator and being operable to determine a reflectance characteristic associated with the surface plane that is based on the reflected electromagnetic energy from the surface plane. The electromagnetic energy controller also includes a motor provided to effect motion of the chopper.
Technical advantages of the present invention include providing an instrument that is portable and that measures at least one reflectance characteristic of a surface. This would allow, for example, a user of the portable measurement instrument to determine a reflectance characteristic of an object or element in-situ, i.e. without having to remove or otherwise displace the object or element from its natural environment. This could be particularly beneficial in the field of aeronautics where the surface of an aircraft, for example, would yield a reflectance characteristic as determined by the portable measuring instrument while remaining in place. This avoids the dilemma of having to remove a component (or alternatively, having to cut out a sample of the component), such as a wing of an aircraft for example, and positioning the component in a laboratory in order to determine its reflectance characteristics.
Another technical advantage of one embodiment of the present invention is increased accuracy in calculating a reflectance characteristic for an object or element. This is due, in part, to the utilization of multiple angles of incidence being nearly simultaneously reflected at a surface to which reflectance characteristics are sought to be determined. In addition, each angle of incidence has an associated set of frequency bands that operate to provide measurements at four designated frequency ranges within the frequency spectrum. As a result, the portable measuring system of the present invention operates to provide at least eight measurements that may be averaged, synthesized or otherwise processed in order to offer a highly accurate measurement associated with at least one reflectance characteristic of a surface.
Still another technical advantage of one embodiment of the present invention is the use of a chopper that comprises an absorptive portion that provides calibration to the portable measuring system. The absorptive portion absorbs electromagnetic energy and provides a constant point of reference to detectors that measure electromagnetic energy levels as reflected from the surface. These detectors may provide immediate feedback to a processor. The processor may then process the data associated with the absorbed electromagnetic energy and accordingly modify a calibration parameter associated with the portable measuring device. This may in turn result in increased accuracy of the system, while still maintaining a high level of speed in operation of the instrument. This would allow, for example, an operator of the reflectance determination system to quickly and accurately evaluate one or more reflectance properties associated with a given surface and establish whether or not maintenance is required on the surface (or alternatively, that maintenance has been performed adequately on the surface, i.e., within a designated specification).
Embodiments of the present invention, which follow, may enjoy some, all, or none of these advantages. Other technical advantages of the present invention are readily apparent to one skilled in the art from the following figures, the description and the claims.